Plane Figures: Parts of a Straight Line
From wikisori
Contents
Age
6-9.
Materials
- Two strings attached to spools
- Two scissors
- A red felt pen.
Preparation
Presentation
- Again the directress prepares the spools in her hands and invites the child to watch as the line appears.
- What is it? A line...a straight line... a straight line....
- Invite the child to find a point on this straight line and mark it in red.
- The child then takes the scissors to cut the line at the point... this is a straight line... (cut).
- Taking one spool and the point, the teacher extends the string... this is a ray... this is a ray.
- The directress identifies the other ray in the same manner.
- These two rays are equal. a ray starts from a point and goes on to infinity.
- This red point is the origin.
- Therefore a point divides a straight line into two rays.
- With the other spool the situation is repeated, with child identifying a straight line.
- This time the child is invited to make two red points on the line, and to cut the line at the two points simultaneously.
- Before the cut, the line is identified as a straight line.
- After the cut the directress takes on piece at a time.
- This is a ray. This is another ray.
- This is a line segment.
- The two red points on this line segment are called endpoints, because we can't tell which is the beginning and which is the end.
- Therefore two points divide a line into two rays and a line segment.
Control Of Error
Points Of Interest
Purpose
Variation
Classified nomenclature - after the child has put the cards with the corresponding labels, have him put them in order: origin, ray, endpoints, line segment.
Links
Handouts/Attachments